I know 7 weeks post op seems like you should be all recovered and back to yourself, but honestly, you had MAJOR surgery and your body is still working hard to heal. My personal experience was the most of 12 weeks...
You couldn't have prevented how you felt with food poisoning (and honestly it is easier to deal with when you have an ostomy, lol!!!)...output will ALWAYS depend on what your diet consists of...I don't necessarily call it D, just sometimes things a loose/liquid and sometimes they're not. I know my doc would like me to bulk it up, but I know a latte causes fast/liquid output and I'll drink more water later...Many veggies/fruit comes out they way you chewed it...that is its reminder to me to chew better:)
As far as the pain, what number would you assign it? If it is just discomfort and you are not running a fever, maybe you were more active than you thought. You said your stoma is functioning so it isn't a blockage...maybe take it easy today...are you still taking pain meds? Maybe a half or just one will take the edge off.
Let us know how things are going!